OpenFlowMPLS Virtual Ports

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Virtual Ports

Our design philosophy is:

• Have a general scheme independent of a given protocol
• Have a set of actions associated with the virtual port that are within the scope of a lightweight OF switch
• Flexibility, and scalability to handle future needs

Ports

Virtual Ports (VP) fall into the general context of ports on a switch. An OF switch will maintain a Port Table. Each port will be identified with a handle that can be used to index the Port Table (PT).
Each entry on the port will contain:

• the set of actions required to put a packet out on the port
• pointer to port data block (counters etc.)
• parent port (to support a hierarchy of ports)

Port Handle: A port handle is a 32 bit unsigned number, which indexes the Port Table.

The Port Table is comprised of these regions:

• Port 0 is an invalid port.
• First 64K entries are reserved for physical ports
• The next 1G(minus 64K) entries are the Virtual Ports
• The final 3G entries are the Outgoing Port List (OPL)

The Outgoing Port List (OPL) is used for Multicast, and other applications that require replication, for example VPLS. Actions:

Examples of actions associated with flows and interfaces include:

• Push (buffer, size, value)
• Push_MPLS_label (buffer, size, value, BoS, CoS, TTL)
• Pop (buffer, size)
• Pop_MPLS_label (buffer, size, value, TTL)2

In the case ofpush_MPLS_label the label pushed is:

Bottom of Stack (BoS)
This bit indicates the bottom of the stack:

         If (TA<BoS [1]>) {
              BoS = TA<BoS[0]>
         } Else if (EType == MPLS) {
              BoS = Packet_Label<BoS> 
         }         

Class of Service (CoS)
CoS bits are computed as:

           If (TA<CoS [3]>) {
                CoS = TA<CoS [2:0]>
           } Else if (EType == MPLS) {
                CoS = Packet_Label<CoS>
           } else if ((TA<CoS [4]>) && (EType == IP)) {
                 CoS = Packet_IP<ToS>
           } else if (EType == 1Q) {
                 CoS = Packet_1Q<PCP>            
           }

TTL
The Time To Live (TTL) bits are computed as:

           If (TA<TTL[8]>) {
                TTL = TA<TTL[7:0]>
           } Else if (EType == MPLS) {
                TTL = Packet_Label<TTL-1>
           } else (EType == IP) {
                 TTL = Packet_IP<TTL>
           }

Use Case: MPLS

At Ingress: Controller will perform these actions:

1. one Allocate a VP (local to the switch) for the MPLS LSP, say VP1
2. Build the set of actions for the VP. In this case the action is:

Push_MPLS_Lbl (shim buffer, LABEL1 value, BoS = 01b, CoS (take form IP header), TTL (take from IP header))

1. Download the VP to the switch Port Table (PT)
2. Install a Matching Entry in the Flow table:

- Flow = LSP FEC

- Actions:

- Outgoing Port = VP1

At Transit: Controller will perform these actions:

1. Allocate a VP (local to the switch) for the MPLS LSP, say VP1
2. Build the set of actions for the VP. In this case the action is:

- Push_MPLS_Lbl (shim buffer, LABEL2 value, BoS = 10b, CoS (take form MPLS label), TTL (take from MPLS label-1))

1. Download the VP to the switch Port Table (PT)
2. Install a Matching Entry in the Flow Table:
3. EType == MPLS
4. Top Label == LABEL1
5. Actions:

- Pop (buffer shim, 4 bytes)

- Outgoing Port = VP1

At Egress: Controller will perform these actions:

1. Install a Matching Entry in the Flow Table:

- EType == MPLS

- Top Label == LABEL2

- Actions:

- Pop (buffer shim, 4 bytes)

- Rewrite IP TTL from MPLS TTL

- Outgoing Port = As desired for the FEC